Thermal Influence on Hydraulic System Pressure (3.1 Mb .wmv)
When hydraulic fluid is trapped in a closed system, pressure is strongly influenced by heating and cooling of the system.
Thermal Cycling (41 Mb)
Shows operation of the hydraulic system during multiple thermal heating and cooling cycles, both retracted and extended.
A properly functioning spool valve prevents pressure buildup in the Low pressure circuit, even when a pronounced leak from the high side circuit is present.
The spool valve must push the poppet valve off its seat to allow hydraulic fluid back to the reservoir thus allowing the gear to be pushed up by hand.
Hydraulic System Lock-Up due to self-centering spool.
A design change to The 108 series Oildyne pump has introduced an unwelcome failure mode to the 108 series pump. Both high and low circuits can retain pressure simultaneously resulting in total system lock up if the system is subjected to large temperature changes or an internal leak develops.
Removing Spool Centering Springs from post-2003 Lancair pumps. This removes the potential for complete system lock-up due to thermal heating.